Sulfurizing terpenes



Jan. 9, 1951 J. J. ALEXANDER SULFURIZING TERPENES Filed April 30, 1948 Patented Jan. 9, 1951 SULFURIZIN G TERPENES John J. Alexander, Munster, Ind., assigner to Standard Oil Company, Chicago, Ill., a corporation of Indiana Application April 30, 1948, Serial No. 24,285

(Cl. 26th-139) 8 Claims. l

This invention relates to an improved method of sulfurizing terpenes with elemental su fur.

Terpenes have heretofore been sulurized with elemental sulfur by mixing the terpene with sulfur and heating the mixture to the desired reaction temperature. Another method heretofore employed is to heat the terpene to the reaction temperature while adding the required amount of sulfur thereto in incremental amounts. These methods of sulfrrzing terpenes are not sati-fac tory in that it is extremely diiiicult to regrlate the temperature or to control the rate of reaction due to the exothermic nature of the reaction. The incremental or continuous addition of sulfur to the reaction involves many dif'dcu'ties since the light terpenes reflux at the reaction temperature and the condensate :'mpdes the addition of dry sulfur. Because of diiculties encountered in controlling the exothermic raction when ter-` penes are sulfur-med by the methods just described, the sulfurized terpenes are very dark in color.

An improved method of sulfurizing terpenes with elemental sulfur is drscrlbed and-claimed in a copending aoplicaton of Roger W. Watson, Serial No. 665,291, led Aprii 23, 1948, which issued as Patent No. 2,445,983 on July 27, 1948, in which terpenes are sulfurized by adding liquid terpenes to molten sulfur. In this method a small amount of the terpene is introduced into the heated sulfur as a diluent during the viscous sulfur stage encountered in heating sulfur to the reaction temperature of about 375 F. to about 400 F. This viscous sulfur stage is enwuntered at a tm perature of about 330 F. The necessity of heating a small amount of terpene with the s lur through the viscous sulfur stage to the reaction temperature of about 340 F. to about 383 F. results in a darkening of the finished sulfur'med terpene.

It is an obiect of the present invention to provide a method of sulfuriz'ing terpenes b v introducing ternenes into molten sulfur which will avoid the darkening of the sulfurized terpenes.

It is another object of the present invent'on to provide a method of sulfurizing terpenes in which the exothermc reactioncan be controlled and a sulfurized terpene product of improved color obtained.

Other objects and advantages of the present invention will become lapparent from the following description thereof read in conjunction with the accompanying drawing, which is a flow diagram of a. preferred method of carrying out the presentv invention.

I have discovered that the foregoing objects can be attained by a method of .suliurization in which the terpene is in the liquid phase to a body of molten sulfur at a certain optimum. temperature, maintained in a non-viscous .condition by the addition of a small amount of liquid terpenes which are not sulfurized, under the sulfurizaton conditions, or which if sulfurized, are readily desulfurized under the deactivation conditons hereinafter described, and which have boiling points below that of the desired sulfurized terpene. A suitable material is the distillate obtained in the fractionation oi terpenes previously sulfurlzed by the addition of liquid terpenes to molten sulfur as hereinafter described. The distillate comprises essentially unsulfurized terpenes, such as para-cymene and paramenthane, and a very small amount, namely less than about 2%, of low-boiling sulfurized terpenes. The .tei-penes which can be sulfurized by the herein described method include monocyclic, bicyclic and acyclic terpenes, as Well as polyterpenes. Exrmg' les of species falling within these classes of terpenes are pine oil, turpentine, alphapinene, beta-pinene, allo-oeimene, fenchenes, bornylenes, menthadienes, such as lmonene, dipentene, terpinene, terpinolenes and 2A,(8) -pmenthadiene, sesquiternencs, diterpene, and polyterpenes having the general formula (C5H8). Mixtures oi such terpenes can also beernployed in the invention. In accordance with the present invention, elemental stfliur is stirred at a temperature above its melting point, for example at a temperature of from about 325 F. to about 400 F., and preferably at a temperature of from about 340 F. toabout 330 F., and the terpenes slowly added in the liquid phase to the molten sulfur.

Depending upon the intended use of the sulfurized terpene, any amount of sulfur can be employed in the sulfurization of the terpene by the herein-described method. However, for the reparation of sulfurized terpenes as a lubricant additive, the sulfur-terpene reaction mixture should contain from about 25% to about 50%, and preferably about 40% by Weight of sulfur, and from about 50% to about '75%, and prefer-- ably about by weight of the terpene.

Sulfur, when heated to a temperature of from about 300 F. to 340 F., enters a so-called vis cous stage. To facilitate adequate stirring during this stage, when the molten sulfur reaches a temperature of from about 300 F. to about 340 F., and preferably from about 300 F. to about 325 F., a small amount, namely from about 3% to about and preferably from about 5% to about 7% by Weight based on the sulfur of a distillate from sulfurized terpenes as hereinafter described, is added to the molten sulfur and the temperature then raised to the desired reaction temperature, namely 340 F. to about 400 F., and the terpene to be sulfurized added.

The sulfurized terpenes contain some active sulfur, as evidenced by the darkening of a copper strip submerged in about 0.5 solution of the sulfurized terpenes in a hydrocarbon oil maintaintd at a temperature of about 210 F. For certain uses, such as lubricatingoil additives, the presence of such active sulfur compounds in the sulfurized terpenes is undesirable. These socalled active sulfur compounds can be deactivated by treating the same with an alkali metal sulfide, such as sodium sulfide or with a mixture of an alkali metal sulde and a small amount of an alkaline material such as, for example sodium hydroxide.

After the sulfurization reaction is completed, which will take about 5 minutes to about 60 minutes or more, and usually about minutes, the sulfurized terpene is rendered non-corrosive by deactivation by the addition of an alkali metal sulde, such as sodium sulfide, preferably added as an 18% aqueous solution. It will be understood that the time of sulfurization is dependent largely upon the rate of refluxing and other cooling means for controlling the exothermic reaction. During the deactivation stage the reaction mixture is maintained at a temperature from about 200 F. to about 260 F., and preferably at about 230 F. It is desirable during the deactivation stage to maintain the reaction mixture under a pressure sufficient to retain the light ends of the product, usually a pressure of about seven pounds will be found to be suicient for this purpose. While it is desirable to carry out the deactivation at the preferred temperature of about 230 F., and a pressure of about seven pounds, higher or lower temperatures and pressures may be employed. After the sulfurized terpene reaction product is deactivated, such as by treatment with the sodium sulfide, the reaction mass is permitted to separate into an upper layer comprising the sulfurized terpenes and a lower layer comprising sodium polysulde solution. After the sodium polysulfide solution layer is separated from the sulfurized terpene product the latter is washed at a temperature of from about 200 F. to about 250 F., and preferably at about 220 F. with a 20% sodium chloride solution. 'Ihe brine solution is then settled and drawn off. The washed deactivated sulfurized terpene product is then ltered and again washed with a 20% sodium chloride solution to remove the last traces of alkali metal polysulfide from the sulfurized product. If desired, the sulfurized terpene product can then be ash distilled, preferably under reduced pressure, to remove any unreacted hydrocarbons or slightly sulfurized lighter terpenes, preferably using an inert gas, such as nitrogen for stripping. In order to avoid the darkening of the sulfurized terpene product, it is essential that the material be held at a temperature of from about 250 F. to about 350 F., and preferably at about 300 F., for a period of time no longer than about 30 to 35 minutes.

The following description of sulfurizing a mix ture of terpenes comprising from about 60% to 65% menthadienes of which a major proportion is dipentene, and small amounts of terpinoline,

terpenes and 2,4(8) menthadienes and about 30% to 35% para-cymene and para-menthane, is given by way of example only and is not to be construed as limiting the scope of the invention.

Referring to the accompanying drawing, elemental sulfur forming about 40% by weight of the sulfurized reaction mixture, is introduced from sulfur storage tank I0 through a line II to the jacketed reactor I 2 provided with a jacket I3, heating means such as superheated steam introduced through a line I4, and a temperature control means I5. If desired, the reactor I2 may be provided with a Dowtherm boiler to supply the necessary heat. The jacketed reactor I2 is provided also with cooling means such as, for example, water inlet and outlet I6 and I1, respectively. After the required amount of sulfur is added to the reactor I2, it is heated to a temperature of from about 300 F. to about 330 F., at which time about 5% to about 7% by weight of a diluent, the composition of which is hereinafter described, from distillate storage tank I8 is introduced, in the liquid phase, into the reactor I2 through the line I9, pump 20 and lines 2l and 22, and the mixture stirred or agitated by means of stirrer 23 0r other suitable means. The distillate (herein referred to as diluent) from storage tank I8 comprises essentially unreacted or unsulfurized terpenes, such as paracymene and para-menthane, together with a small amount of sulfurized low-boiling terpenes resulting from the fractionation of terpenes previously sulfurized in accordance with the present invention as hereinafter described. While it is advantageous to employ as the diluent, the distillate fraction such as described, obviously the present invention can be practiced by employing as a diluent preceding tbe viscous sulfur stage, small amounts of terpenes from any source and which are not readily sulfurized. After the addition of the diluent to the reactor I2, the temperature of the contents of the reactor is increased to a temperature of about 340 F.-380 F., and terpenes, in the liquid phase, from terpene storage tank 24 introduced into the reactor as rapidly as possible through pump 20 and lines 2| and 22. The quantity of terpene employed amounts t0 about 60% by weight of the sulfur terpene reaction mixture. During this period the temperature within the reactor is maintained within the range of from about 340 to 380 F., suitably by means of a reflux condenser 25. The hydrogen sulfide formed is vented from the reactor I2 through a line 26.

The sulfurized terpene mixture is then deactivated by treatment with an 18% aqueous solution of sodium sulfide from tank 21 introduced into the reactor I2 via pump 28 and line 29. From about 10% to about 20%, and preferably 14% to 15% by Weight of sodium sulfide is usually suicient to deactivate the sulfurized terpene product. During the time the sulfurized terpene reaction product is being deactivated with the sodium sulde, a temperature of about 230 F. is maintained in the reactor by passing steam into the jacket I3. The mixture of sulfurized terpene reaction products and sodium sulfide is stirred at the proper temperature for 'a period of about two hours while maintaining a pressure of about seven pounds upon the reactor to retain the light ends. At the end of the two hour deactivation period, the reaction mass in reactor I2 is permitted to stratify into an upper layer comprising the deactivated sulfurized terpene product. and a lower layer of sodium polysulde solutin',"and the-latter drawn off through lines 22': and'V 30: `tov la Asodium polysuliide storage tank 3I`.

After the sodium poly'suliide solution' is withdrawn from-the reactor I2,`the deactivated sulfurized""terpene iswashed with a ...indium chIoride'solution-introduced into the reactor i2 from tank 32-through pump 33 and lines 34 and 28.' The washed deactivated sulfurized ter-pene product-is then-"settled and the sodium chloride drawnfoifthrough lines 22and 3E' to the sewer.

The solid sodium* polysulde remaining in the washed. deactivated sulfurized terpene,4 together with 'any-other solid or colloidal impurities,` are removed by-introduoing the sulfurized terpene via lines22 and 36 and pump 31 to a suitable lt'er 3S, whchmay be a-Sparkler type filter. Filter 38 is maintained, by suitable means, at a temperature of about l320`^F. and operated at a pressure of about 'twenty'pounds-'per square inch. It has be'eufoiind that a filter rate of 121/2 gallons per hour per square foot is suitable. Lower or higher pressuresor temperatures can of course be ernployed .but with some'sacrifice in efliciency.

Tiiltrate from the lter'38 is passed via line Mito a wash drum 40 'provided with stirring means wherein'the'iiltered sulfurized terpene iswashedone or'more times withl a 20% sodium chloride solution from tank 32;via pump 33. and lines 34' and' 42, to' remove' the last traces .of sodiiim polysulde. The` sodium chloride solution in Washtank 40 is Withdrawn via line i3 to tanl; 44. Th'e' used sodium chloride solution may be dumped to thesewer, or if a plurality of was-es are used. the last wash may be recycled to the wash' drum` foi' the washing of4 the next batch.

The washed filtered sulfurized terpene from wash tank ntis'passed via4 pump 45 and lines 46 and 41 to a. preheater 48 wherein the sulfuriz `d terpeneisheated to a temperature of about 308 F3, and then .introduced into a stripping tower 48. wherein .the heated sulfurized terpene is alsh distillectat about 50 mm.' pressure and with sufficient nitrogen purge gas', introduced from nitrogen supply tank 50 via line 5I, to reduce the sulfurized terpene product to a bottoms fraction having the desired sulfur content. If desired, a portion of the nitrogen from tank 50 maybe introduced via lines 5I and 52 to line il introduced into the stripping tower 49, together with the sulfurized terpene. The stripping tower '23 may be provided with heating and/or cooling coils 53.

The amount of nitrogen used is that necessary for maintaining agitation within the sfriprer 49 and for removing the light ends in the bottoms. An overhead fraction is taken from the stripper 49 via line 54 and condenser 55 to a separator drum 56, from which uncondensables are withdrawn via vacuum pump 51 and line 58. Unreacted terpenes and sulfurized low-boiling terpene products recovered as overhead from the stripping tower 49 are removed from separator drum 58 via pump 59 and line 60 to the storage tanl: I8.

The unreacted terpenes, and sulfurized lowboiling terpene products in tank I8, are recycled through line I9, pump 20, and lines 2I and 22 to the reactor I2, as a diluent for the molten sulfur, as hereinbefore described.

The bottoms from the stripper 49, comprising essentially the desired sulfurized terpenes are withdrawn via pump 6I, passed through a cooler exchanger 62 and through line $3 to storage tank 64.

The filtered. sulfurized terpene, after the sodium chloride wash 'in wash drum 40,'may be usedasza a lubricant additive. It is desirable'to remove the. light ends of the product and concentratethe bottoms to a sulfur content of from'-about-30%" to about 50%, and preferably about 40%.' Suliurized terpenes, preferably sulfurized dipentene having a sulfur content within this range, are suitably employed as lubricant additives to inhibit corrosion and as extreme -pressure agents;

By conducting the sulfurization of terpenes in the manner herein described, heating sulfurizable terpenes in the presence of sulfur at elevated ternperatures over prolonged periods is avoided. This avoids the possible formation of dark colored sulurized terpene products with the -result that the sulfurized terpenes obtained by the present invention are of improved color. Other advantages' obtained are that the heat taken up by the in'- coming terpene such as dinentene helps to' control f-the speed of reaction. Furthemcre, introducing the terpene at substantially reaction temperature results in substantially instant sulfurization so that substantially no polymerization or -resiniii-- cation takes place.

While I have described. in detail the 'preferred embodiment of my invention it should be understood that the invention is not limited to the deltails herein-above set forth, except as dened 'by the appended claims.

Iclaim:

`1. In the method of sulfurizing terpenes wherein elemental sulfur is heated 'to a-molten-temperature offrotn about 325 F. to about 400 F., and a snlfurizable liquid terpene introduced into said sulfur and the mixture maintained at said temperature for a time suflicient toI complete the' sulfurization of said terpenes, the improvement comprising heating the sulfur to a temperature of from about 300 F. to about 340 F., intro" ducing into said heated sulfur a small amount of a liquid consisting of terpenes which'are not sulfurized under said sulfurization .conditions and which boil below the boiling point of the desired sulfnrized terpene, whereby said molten sulfur is maintained in a fluid state, increasing the temperature of the mixture to about 340 F. to about 400 F., and introducing into said molten sulfur the sulfurizable liquid terpene to be sulfurized.

2. in the method of sulfurizing terpenes wherein sulfur is heated to a molten temperature of from about 325 F. to about 400 F., and sulfurizable liquid terpenes introduced into said molten sulfur and the mixture maintained at said temperture for a time suicient to effect the sulfurizaion of said terpenes, the improvement comprising heating the sulfur to a molten temperature of about 300 F. to about 325 F., introducing a small amount of a liquid consisting of terpenes which are not sulfurized under sulfurization conditions and which have boiling points below that of the desired sulfurized terpene product, whereby said molten sulfur is maintained in a fluid state, increasing the temperature of the mixture to a temperature above about 340 F. but below about 400 F., introducing sulfurizable liquid terpenes to 'be sulfurzed in said molten sulfur and maintaining said temperature for a time suicient to substantially complete the sulfurization of said last named terpenes.

3. The method of sulfurizing terpenes as described in claim 2 in which the sulfurizable terpenes to be sulfurized comprise essentially dipentene.

4. In the process of sulfurizing terpenes with elemental sulfur wherein elemental sulfur is heated to a'temperature above its melting point but below about 400 F., a mixture of sulfurizable and unsulfurizable liquid terpenes introduced in said molten sulfur and maintained at said temperature for a time sufficient to substantially complete the sulfurization of said sulfurizable terpenes, the mixture of sulfurized terpenes and unsulfurized terpenes fractionated to obtain a bottoms fraction consisting essentially of substantially entirely of the sulfurized terpenes, and a distillate fraction consisting essentially of lower boiling unsulfurized terpenes and a small amount of low-boiling sulfur-ized terpenes the improvement comprising introducing a. small amount of said distillate into a subsequent batch of molten elemental sulfur heated at a temperature of from about 300 F. to about 325 F., increasing the temperature of the mixture of molten sulfur and distillate to above 350 F., but below about 400 F., and introducing sulfurizable liquid terpenes in said mixture, maintaining the reaction mixture at such a temperature above 350 F., but below 400 F. for a time sufficient to substantially complete the sulfurization of said last named terpenes.

5. The method of sulfurizing terpenes as described in claim 4 in which the sulfurizable terpenes are a mixture of menthadienes and the recycled distillate consists essentially of unsulfurized cymene and menthane.

6. The method of sulfurizing terpenes as described in claim 4 in which the mixture of sulfurizable and unsulfurizable liquid terpenes are amixture comprising a, major proportion of di-v pentene, and small amounts of terpinoline, 2, 4,(8) menthadienes, para-cymene and paramenthane and the recycled distillate consists essentially of unsulfurized para-cymene, unsulfurized para-menthane and a, small amount of low-boiling sulfurized terpenes distillable at a temperature of about 300 F. at about 50 mm. pressure.

7. The method of sulfurizing terpenes comprising heating a body of elemental sulfur to a temperature of about 300 F. to about 325 F.,

adding a, small amount of terpenes consisting essentially of para-cymene and para-menthane, which are not sulfurized under sulfurization temperatures of 340 F. to 380 F., heating the mixture to a temperature of 340 F. to about 380 F., adding a mixture of sulfurizable andunsulfurizable terpenes to the heated mixture, maintaining the mixture at a, temperature of about 340 F. to about 380 F. for a time sucient to substantially complete the sulfurization of the sulfurizable terpenes in said terpene mixture, reducing the temperature of the reaction mass to a temperature of from about 200 F. to about 250 F., adding an alkali metal sulde to the reaction mixture to remove corrosive sulfur coml pounds therefrom in the form of polysuldes, separating the polysuldes from the reaction mixture, distilling the alkali metal sulfide-treated reaction product at a temperature of about 300 F. at about mm. pressure, to obtain a bottoms fraction comprising essentially a sulfurized terpene product containing from about 30% to about 50% sulfur and a distillate fraction comprising essentially low-boiling unsulfurized terpenes and low-boiling sulfurized terpenes, and recycling a portion of said distillate to a body of molten sulfur heated at a temperature of about 300 F. to about 325 F. to maintain said body of sulfur in a non-viscous fluid state.

8. The method of claim 'I in which the sulfurizable terpenes comprise essentially dipen-- tene.

JOHN J. ALEXANDER.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,349,909 Pratt Aug. 17, 1920 2,156,919 Merriam May 2, 1939 2,443,823 Holt June 22, 1948 2,445,983 Watson July 27, 1948 

1. IN THE METHOD OF SULFURIZING TERPENES WHEREIN ELEMENTAL SULFUR IS HEATED TO A MOLTEN TEMPERATURE OF FROM ABOUT 325* F. TO ABOUT 400* F., AND A SULFURIZABLE LIQUID TERPENE INTRODUCED INTO SAID SULFUR AND THE MIXTURE MAINTAINED AT SAID TEMPERATURE FOR A TIME SUFFICIENT TO COMPLETE THE SULFURIZATION OF SAID TERPENES, THE IMPROVEMENT COMPRISING HEATING THE SULFUR TO A TEMPERATURE OF FROM ABOUT 300* F. TO ABOUT 340* F., INTRODUCING INTO SAID HEATED SULFUR A SMALL AMOUNT OF A LIQUID CONSISTING OF TERPENES WHICH ARE NOT SULFURIZED UNDER SAID SULFURIZATION CONDITIONS AND WHICH BOIL BELOW THE BOILING POINT OF THE DESIRED SULFURIZED TERPENE, WHEREBY SAID MOLTEN SULFUR IS MAINTAINED IN A FLUID STATE, INCREASING THE TEMPERATURE OF THE MIXTURE TO ABOUT 340* F. TO ABOUT 400* F., AND INTRODUCING INTO SAID MOLTEN SULFUR THE SULFURIZABLE LIQUID TERPENE TO BE SULFURIZED. 